Range maximization of a hybrid vehicle operating in an electric vehicle operating state

ABSTRACT

A vehicle has a powertrain including an engine and at least one electric machine. A method for maximizing range capability of the vehicle while operating in an electric vehicle operating state includes determining an incipient electric vehicle operating state of the powertrain, setting a preferred charge/discharge rate of an electric energy storage device to a maximum charging rate, and controlling the powertrain to an operating state including an engine state that is ON to effect charging the electrical energy storage device based on the maximum charging rate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application No.60/861,638, filed on Nov. 28, 2006, which is hereby incorporated hereinby reference.

TECHNICAL FIELD

This disclosure pertains to hybrid powertrain systems.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Powertrain architectures for vehicles comprise torque-generativedevices, including internal combustion engines and electric machines,which transmit mechanical torque through a transmission device to anoutput. Known engines can also generate torque which may be transmittedto the electric machine to generate electric power, which is storable aselectrical energy potential in an on-board electrical energy storagedevice. An electrical energy storage device can be electrically coupledto a remote power supply for electrical charging during a period whenthe vehicle is static, e.g., parked.

SUMMARY

A vehicle has a powertrain including an engine and at least one electricmachine. A method for maximizing range capability of the vehicle whileoperating in an electric vehicle operating state includes determining anincipient electric vehicle operating state of the powertrain, setting apreferred charge/discharge rate of an electric energy storage device toa maximum charging rate, and controlling the powertrain to an operatingstate including an engine state that is ON to effect charging theelectrical energy storage device based on the maximum charging rate.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may take physical form in certain parts and arrangementof parts, embodiments of which are described in detail and illustratedin the accompanying drawings which form a part hereof, and wherein:

FIGS. 1 and 2 are schematic diagrams of exemplary powertrain and controlsystems, in accordance with the present disclosure;

FIG. 3 is a schematic diagram of a logic flowchart, in accordance withthe present disclosure; and

FIGS. 4, 5 and 6 are schematic diagrams of exemplary powertrain systems,in accordance with the present disclosure.

DETAILED DESCRIPTION

Referring now to the drawings, wherein the depictions are for thepurpose of illustrating certain exemplary embodiments only and not forthe purpose of limiting the same, and wherein like elements among theexemplary embodiments and drawings are numbered alike, FIG. 1 depicts anembodiment of a powertrain system 10A and control system 15 operative totransmit torque to a transmission output member 64, e.g., to atransmission output shaft, which is connected to a driveline 90 of avehicle. The powertrain system 10A includes an internal combustionengine 20 and an electro-mechanical transmission 30A including a firstelectric machine (‘MG-A’) 40, a second electric machine (‘MG-B’) 50, anda planetary or parallel shaft reduction gear set (‘PG’) 34. The firstand second electric machines 40 and 50 are depicted as being integratedinto the transmission 30A, although the disclosure is not so limited. Anelectric energy storage device (hereafter ‘ESD’) 60 is electricallycoupled to an inverter module (‘IM’) 45, described hereinbelow, and anESD charging device 70. The ESD charging device 70 is selectivelycoupled to a remote electric power supply 80 via an electrical connector72 when the vehicle is in a static position. The engine 20 operativelycouples to the first electric machine 40 via a transmission input shaft24 to generate electric power. The second electric machine 50operatively couples to the transmission output member 64 via the gearset 34 as shown, or directly without an intervening gearset. The secondelectric machine 50 may transmit tractive torque through thetransmission 30A to the driveline 90 for vehicle propulsion and forregenerative braking. The driveline 90 may comprise a front-wheel drivesystem including a transaxle and half-shafts connected to drive wheels,a rear-wheel drive system including a differential and axles connectedto drive wheels, and other driveline configurations, none of which areshown in detail.

The control system 15 provides coordinated system control of thepowertrain system 10A by controlling operation of the engine 20,transmission 30A, and the first and second electric machines 40 and 50,including controlling operation of the powertrain system 10A in one of aplurality of powertrain operating states. The control system 15comprises a hybrid control module (hereafter ‘HCP’) 12, an enginecontrol module (hereafter ‘ECM’) 22, transmission control module(hereafter ‘TCM’) 32, motor control module (hereafter ‘MCP’) 52, andbattery pack, or ESD control module (hereafter ‘BPCM’) 62. The controlsystem 15 receives operator demands and other inputs from an operatorinterface module (‘UI’) 14 via a local area network (hereafter ‘LAN’)bus connection 16.

Transmission 30A selectively transmits power among the engine 20, thefirst electric machine 40, the second electric machine 50, and thedriveline 90 via the gear set 34, including selectively applying torquetransfer devices, hereafter referred to as clutches (not shown) butintended to include all varieties of torque transfer devices including,for example, wet and dry clutches, band clutches, and brakes. Thetransmission 30A is controlled by the TCM 32. The TCM 32 is signally andoperatively coupled to the transmission 30A and functions to acquiredata from sensors (not shown) and provide command signals. The TCM 32determines clutch torques, monitors rotational output speed from atransmission output sensor (not shown), and monitors outputs fromhydraulic pressure sensing devices (not shown) in the transmission. TheTCM 32 selectively controls pressure control solenoids (not shown) andshift solenoids (not shown) to control the torque transfer clutches toachieve one of the powertrain operating states.

The engine 20 preferably comprises a multi-cylinder internal combustionengine operative to generate and transmit torque to the first electricmachine 40. The engine 20 can be of a spark-ignition type, acompression-ignition type, or other operating cycle, utilizing availablefuels, including but not limited to gasoline, diesel, and alcohol-basedfuels. The engine 20 is controlled by the ECM 22, which is signally andoperatively coupled to the engine 20, and functions to acquire data froma variety of sensors (not shown) and control a variety of actuators (notshown) over a plurality of discrete lines (not shown). Acquired dataincludes input from a crankshaft position sensor (not shown) to provideengine speed. Other parameters sensed by ECM 22 include engine coolanttemperature, manifold pressure, ambient air temperature, and ambientpressure, all of which are not shown. Various actuators that may becontrolled by the ECM 22 include fuel injectors, ignition modules, andthrottle control modules, all of which are not shown. The ECM 22 isoperative to control the engine 20 to engine states comprising an engineon state (‘ON’), i.e., the engine is fueled and firing, and an engineoff state (‘OFF’), i.e., the engine is not fueling and is not firing.The ECM 22 can shut off and subsequently restart the engine 20 duringongoing vehicle operation. The ECM 22 communicates with other controlmodules via the LAN bus 16.

The first and second electric machines 40 and 50 are three-phase ACelectric machines electrically coupled to and controlled by the invertermodule 45. The first electric machine 40 preferably comprises a rotor(not shown) and stator (not shown), with the rotor operatively connectedto the transmission input shaft 24 and the stator grounded to a case(not shown) of the transmission 30A. The second electric machine 50preferably comprises a rotor (not shown) and stator (not shown), withthe rotor operatively connected to the transmission output member 64 viathe gear set 34 as depicted, although the disclosure is not so limited.The stator is grounded to the case of the transmission 30A.

The inverter module 45 is high voltage DC-coupled to the ESD 60 viatransfer conductors 61. The inverter module 45 preferably comprises apair of complementary three-phase power inverters (not shown) adapted totransmit electric power to and from the first and second electricmachines 40 and 50 via transfer conductors 41 and 51 respectively. Thethree-phase power inverters each preferably comprises a plurality ofsemiconductor power switching devices, e.g., insulated gate bipolartransistors (‘IGBTs’) (not shown) that form a switch mode power supplyconfigured to receive control commands from the MCP 52. There istypically one pair of IGBTs for each phase of each of the three-phaseelectric machines. States of the IGBTs are controlled to provide motordrive or electric power regeneration functionality. The three-phaseinverters receive (or supply) DC electric power via transfer conductors41 and transform it to (or from) three-phase AC power, which isconducted to (or from) the first and second electric machines 40 and 50for operation as motors (or generators).

The MCP 52 controls the inverter module 45 to achieve desired motortorques. The MCP 52 controls the IGBTs of the inverter module 45 tocontrol transmission of electrical power to and from the first electricmachine 40 via transfer conductors 41, and to control transmission ofelectrical power to and from the second electric machine 50 via transferconductors 51. Electrical current is transmitted to and from the ESD 60via transfer conductor 61 in accordance with whether the inverter module45 is charging or discharging the ESD 60 during vehicle operation.

The ESD 60 comprises a high-voltage electrical energy storage device,(e.g., one or more batteries or ultracapacitors, or combinationsthereof), preferably batteries for storing and supplying electricalenergy for use during operation of the powertrain. The BPCM 62 issignally coupled to one or more sensors (not shown) for monitoringelectrical current, voltage, and temperature of the ESD 60 to determineparametric states of the batteries. Such parametric states includebattery state of charge, amp-hour throughput, voltage, availableelectrical power, and device temperature. The ESD 60 is electricallycoupled to ESD charging device 70 which is couplable via the electricalconnector 72 to the remote electric power supply 80 when the vehicle isin a static position. The ESD charging device 70 converts AC electricalpower to DC electrical power and transfers it to the ESD 60. Theelectric connector 72 may electrically couple current ohmically throughconductive contacts or inductively through known inductive couplingdevices. Known remote electric power supplies 80 include a stationaryelectrical grid for supplying electric power to residential andcommercial consumers.

The operator interface module 14 is operatively coupled to a pluralityof devices through which demands from the vehicle operator aredetermined to control and direct operation of the powertrain system 10A.The devices may include an accelerator pedal (‘AP’) and a brake pedal(‘BP’) from which an operator torque request is determined, atransmission gear selector (not shown), and a vehicle speed cruisecontrol (not shown). The transmission gear selector has a discretenumber of operator-selectable positions, including direction of thetransmission output member 64, i.e., one of a forward and a reversedirection. An operator interface device (‘OID’) 18 may include a controlpanel comprising a plurality of elements, e.g., a touch-activated visualdisplay screen, operator selectable or operator-adjustable buttons,switches, and knobs, none of which are shown. The operator interfacedevice 18 is preferably located in a console accessible to the vehicleoperator, and receives control inputs from the operator, including aninput requesting powertrain operation in an electric vehicle (‘EV’)operating state, and communicates information to the operator. Theoperator interface device 18 can be an element of an on-board navigationsystem which can include a global positioning system (GPS), and awireless communications system, none of which are shown. The on-boardnavigation system and global positioning system can provide signalinputs to the control system 15 useable for operating the powertrainsystem 10.

The HCP 12 provides supervisory control of the powertrain system,serving to coordinate operation of the ECM 22, TCM 32, MCP 52, and BPCM62. These control modules comprise a subset of an overall vehiclecontrol architecture, and comprise the control system 15 which providescoordinated system control of the powertrain system 10. As described indetail hereinbelow, the control system 15 synthesizes the inputs todetermine operator demands and operating conditions, and executesalgorithms to control various actuators to achieve control targets forcertain parameters including fuel economy, emissions, performance, anddrivability, and to protect powertrain system hardware. Based uponvarious input signals from the operator interface module 14 and thepowertrain, including the ESD 60, the control system 15 generatesvarious commands, including: the operator torque request; a commandedoutput torque to driveline 90; the engine input torque; clutch torquesfor the torque transfer clutches of the transmission 30; and motortorque commands for the first and second electric machines 40 and 50.

The aforementioned control modules may communicate with other controlmodules, sensors, and actuators via the LAN bus 16, as described herein.The LAN bus 16 facilitates structured communication between the variouscontrol modules consisting of sensor outputs, control parameters, anddevice commands. The communication protocol utilized isapplication-specific. The LAN bus 16 provides for robust messaging andinterfacing between the aforementioned control modules, and othercontrol modules providing functionality such as antilock brakes,traction control, and vehicle stability. Multiple communications busesmay be used to improve communications speed and provide signalredundancy and integrity.

Each of the aforementioned control modules is preferably ageneral-purpose digital computer comprising a microprocessor or centralprocessing unit, storage mediums comprising read only memory (‘ROM’),random access memory (‘RAM’) and electrically programmable read onlymemory (‘EPROM’), a high speed clock, analog to digital (‘A/D’) anddigital to analog (‘D/A’) circuitry, and input/output circuitry anddevices (‘I/O’) and appropriate signal conditioning and buffercircuitry. Each control module has a set of control algorithms,comprising resident executable program instructions and calibrationsstored in ROM and executed to provide the respective functions of eachcomputer. Information transfer between the various computers ispreferably accomplished using the aforementioned LAN bus 16.

Algorithms for controlling the powertrain system 10 and estimatingparametric states are executed during preset loop cycles such that eachalgorithm is executed at least once each loop cycle. The algorithms arestored in the non-volatile memory devices, and are executed by one ofthe central processing units to monitor inputs from the sensing devicesand execute control and diagnostic routines to control operation of therespective device, using preset calibrations. Loop cycles are executedat regular intervals, for example each 3.125, 6.25, 12.5, and 100milliseconds during ongoing engine and vehicle operation. Alternatively,algorithms may be executed in response to occurrence of an event.

The powertrain system 10A depicted with reference to FIG. 1 isselectively operative in one of several powertrain operating states bycontrolling the engine state and operating the second electric machine40 to generate tractive torque which can be transmitted to the driveline90, as detailed in Table 1.

TABLE 1 Powertrain Operating State Tractive Torque Generator EngineState EV second electric machine OFF EV-C second electric machine ON CNo tractive torque generation ON

In an electric vehicle (‘EV’) operating state, the second electricmachine 50 generates the tractive torque, and the engine state is OFF.The engine 20 and first electric machine 40 are preferably disconnectedfrom the transmission output member 64. In an electric vehicle withcharging (‘EV-C’) operating state, the second electric machine 50generates the tractive torque, and the engine state is ON, generatingpower for charging the ESD 60 via the first electric machine 40. In acharging (‘C’) operating state, the engine state is ON, generating powerfor charging the ESD 60 via the first electric machine 40, and there isno tractive torque generated. Electrical power can be regenerated duringbraking or coasting events, regardless of the powertrain operatingstate.

FIG. 2 depicts a second embodiment of a powertrain system 10B and thecontrol system 15. The powertrain system 10B includes the engine 20 andan electro-mechanical transmission 30B including first and secondelectric machines 40 and 50, a gear set (‘PG’) 34′, which preferablycomprises a planetary gear set, and selectively engageable clutches A,B, and C. A first gear member of the gearset 34′ is connected to thesecond electric machine 50. A second gear member of the gearset 34′ isconnected to the transmission output member 64. A third gear member ofthe gearset 34′ may be selectively connected to the transmission case(i.e. grounded) by applying clutch A. The third gear member of thegearset 34′ may be selectively connected to the first electric machine40 by applying clutch B. And, the engine 20 is connected to thetransmission input member 24 which may be selectively connected to thefirst electric machine 40 by applying clutch C.

The powertrain system 10B depicted with reference to FIG. 2 isselectively operative in one of several powertrain operating states bycontrolling the engine state and operating the first and second electricmachines 40 and 50 to generate tractive torque which can be transmittedto the driveline 90 through selectively applied clutches, as detailed inTable 2.

TABLE 2 Powertrain Operating Clutch State Applied Tractive TorqueGenerator Engine State EV1 A second electric machine OFF EV2 B first andsecond electric OFF machines EVT B, C engine, first and second ONelectric machines EV1-C A, C second electric machine ON Charging C Notractive torque ON generation

In a first electric vehicle (‘EV1’) operating state, the second electricmachine 50 generates the tractive torque transmitted to the driveline90, and the engine state is OFF. The engine 20 and first electricmachine 40 are preferably disconnected from the transmission in anelectric vehicle operating state. In a second electric vehicle (‘EV2’)operating state, the first and second electric machines 40 and 50generate the tractive torque, and the engine state is OFF. In anelectrically variable transmission (‘EVT’) operating state, the enginestate is ON, and the engine 20 and the first and second electricmachines 40 and 50 generate the tractive torque. In a first electricvehicle with electric charging (‘EV1-C’) operating state (alternativelyreferred to as series hybrid operating state), the second electricmachine 50 generates the tractive torque. The engine 20 and firstelectric machine 40 are disconnected from the driveline 90, and theengine state is ON, generating power for charging the ESD 60 through thefirst electric machine 40. In a charging operating state, the enginestate can be ON, and the engine 20 generates power for charging the ESD60 through the first electric machine 40, and is disconnected from thedriveline 90, i.e., no tractive torque is transmitted to the driveline90 from the engine 20. Furthermore, the first electrical machine 40 canbe controlled to start the engine 20, e.g., in the charging operatingstate. Electrical power can be regenerated during braking or coastingevents, regardless of the powertrain operating state.

FIG. 3 depicts a control routine 200, executable as program codecomprising one or more algorithms in one or more of the control modulesduring the preset loop cycles, to operate the powertrain system 10, suchas the exemplary embodiments shown with reference to FIGS. 1, 2, 4, 5,and 6. Overall the control routine 200 includes determining operatordemands, the current powertrain operating state, and vehicle operatingconditions based upon the operating demands. An operating strategy isselected, based upon the operator demands, the current powertrainoperating state, and the operating conditions. The powertrain system 10is controlled to one of the powertrain operating states to transmitpower, in the forms of driveline tractive torque and electric powergeneration, based upon the operating strategy and the operator demands,the powertrain operating state, and the operating conditions. A personhaving ordinary skill in the art will understand that the controlroutine 200 described herein is applicable to various electro-mechanicalhybrid powertrain configurations, including series-hybrid systems,parallel-hybrid systems, power-split hybrid systems, and others. Thisincludes systems wherein the engine 20 and the first electric machine 40are mounted remotely from the transmission 30.

During vehicle operation, the operator demands are monitored, preferablythrough the operator interface module 14. The current powertrainoperating state and current operating conditions are determined (205).

The control system 15 determines whether the operator demands andoperating conditions dictate selecting an operating strategy thatincludes compelling engine operation (210), which includes setting theengine state to ON (236). The control system 15 may compel engineoperation whenever the available battery power or energy falls belowpreset thresholds, e.g., as determined by the state of charge of the ESD60. The preset threshold for the state of charge of the ESD 60 may bedetermined based upon vehicle speed and the operator torque request.Estimates of available battery power and energy are determined,preferably in the BPCM 62, based on battery information, including thestate of charge, battery temperature, battery age, average temperaturehistory, current depth of discharge, cumulative depth of discharge,cumulative amp-hour throughput, and other factors. Furthermore, thecontrol system 15 may compel engine operation when the temperature ofthe ESD 60 exceeds a preset threshold. Furthermore, the control system15 may compel engine operation to provide cabin heating at low ambienttemperature conditions, to meet operator expectations for comfort.Furthermore, the control system 15 may compel engine operation toprovide system cooling and protect components from overheating, such asthe first and second electric machines 40 and 50 and the inverter module45. Furthermore, the control system 15 may compel engine operationperiodically in accordance with a predetermined schedule tosystematically exercise engine components. This includes operating theengine and engine subsystems, e.g., a fuel system (not shown) tolubricate base engine parts, e.g., pistons and bearings, and cycle theactuators to prevent degradation due to lack of use. Furthermore, thecontrol system 15 may compel engine operation to warm up the exhaustaftertreatment in a controlled manner to achieve or maintain temperatureof an exhaust aftertreatment device (not shown).

After it is determined whether engine operation is compelled, it is thendetermined whether the preferred operating strategy comprises anelectric vehicle range maximization strategy (hereafter ‘EV rangemaximization strategy’) (212, 230). The EV range maximization strategyoperates to maximize range capability in one of the EV operating states,for example subsequent to operating the vehicle in a geographic regionwhereat operation of the engine 20 is permissible. The EV rangemaximization strategy is executed, and one of the EV operating states issubsequently activated as further described herein below. When the EVrange maximization strategy is activated, the control system 15 sets apreferred charge/discharge rate to compel engine operation to charge theESD 60 at a maximum charge rate such that the state of charge of the ESD60 exceeds a predetermined minimum state of charge and is within anallowable range, while meeting all operator commands for torque andauxiliary functions (228, 232). Therefore, the EV range maximizationstrategy includes operation of the engine and charging of the ESD 60 andmay be accomplished in powertrain operating states that are not purelyelectric vehicle operating states (i.e. operating states wherein theengine state is OFF) and include series or parallel hybrid powertrainconfigurations with appropriate power splits to ensure driveline torquerequirements are met, auxiliary power functions are met, and thepreferred charge rate is met. One having ordinary skill in the art willtherefore appreciate that the electric charging operating states and theelectrically variable transmission operating states of the embodimentsillustrated in FIGS. 1 and 2 may be employed in carrying out the EVrange maximization strategy. Similarly, one having ordinary skill in theart will appreciate that alternative powertrain configurations thatinclude fixed gear operating states, such as described herein below withrespect to the embodiments of FIGS. 4-6, may also be employed incarrying out the EV range maximization strategy. One having ordinaryskill in the art will therefore appreciate that in carrying out the EVrange maximization strategy, the powertrain operating state will includean engine state of ON. When the ESD 60 achieves a state of charge withinthe allowable range, preferably corresponding to a relatively high stateof charge, the control system 15 maintains the ESD 60 at that state ofcharge until either the EV range maximization strategy is deactivated oroperation in one of the EV operating states is initiated, either by aninput by the vehicle operator to the operator interface device 18, or byother action related to the vehicle operation. This may or may notdictate that the engine 20 remains constantly on, depending on thepreferred charge rate and the vehicle drive schedule in process. As usedherein, the terms charge rate and charge/discharge rate refer to atime-based rate of electric power flow into or out of the ESD 60,preferably in amp-hours.

The EV range maximization strategy can be activated automatically forexample when an incipient electric vehicle operating state isdetermined. For example, EV range maximization strategy may be activatedwhen the vehicle is proximal to and approaching a geographic area wherevehicles are restricted to EV-only operation, using information from theGPS system and map information which may be made available a priori orobtained via a wireless network while the vehicle is operating.Alternately, the vehicle operator may select and designate one or moregeographic areas as desirable for EV operation via input to the operatorinterface device 18. Alternately, EV range maximization strategy may beactivated if a preset drive path is known which includes portions ofrequired or desired EV-only operation. Alternately, the vehicle operatormay select the EV range maximization strategy via input to the operatorinterface device 18 indicating a preference for operating in the EVoperating state, causing the control system 15 to activate the EV rangemaximization strategy prior to operating in the EV operating state. TheEV range maximization strategy is then activated preceding entry intothe areas of EV operation or in anticipation of the electric vehicleoperating state to achieve a state of charge of the ESD 60 effective topermit operation using a charge depletion operating strategy subsequentthereto.

When the engine 20 is not compelled to operate, and the EV rangemaximization strategy is not indicated, it is determined whether thecharge depletion operating strategy is permitted (214). The controlsystem 15 determines whether there are operating conditions whichprevent depleting the charge of the ESD 60. This includes monitoringhealth and performance of the ESD 60. For example, the charge depletionoperating strategy is not permitted whenever the available power and/orenergy from the ESD 60 fall below a preset threshold. The BPCM 62estimates the available power and energy from the ESD 60 based onbattery information including the state of charge, battery temperature,battery age, average temperature history, current depth of discharge,cumulative depth of discharge, and cumulative amp-hour throughput.

When the charge depletion operating strategy is permitted, it isdetermined whether engine-off operation is preferred (216). The controlsystem 15 monitors and reviews conditions which prevent the engine 20from being compelled to operate by the control system 15. Theseconditions include a default powertrain operating state, wherein thedefault powertrain operating state comprises operating in one of the EVoperating states until the state of charge of the ESD 60 falls below athreshold, i.e., the ESD 60 has been depleted. The vehicle operator mayselect the EV operating state as a preferred powertrain operating stateusing an on-board input device, e.g., selecting EV operation using tothe operator interface device 18. The control system 15 may activate oneof the EV operating states and engine-off operation based upon inputfrom the GPS system to the operator interface device 18, when thevehicle approaches a geographic area where vehicles are restricted toEV-only operation. Alternately, the operator may select and designatespecific areas as desired for EV-only operation, utilizing the GPSsystem and on-board electronic maps made available a priori or obtainedvia a wireless network while the vehicle is operating. Alternately, thecontrol system 15 may activate one of the EV operating states based uponthe operator executing a preset drive path, including portions whichhave required or desired EV-only operation. When the control system 15determines the EV operating state is preferred, the engine state is setto OFF, and the engine is shutdown or continues to be shutdown when itis already shutdown (220).

The charge depletion operating strategy is refined to include apreferred charge/discharge rate for the ESD 60, when engine operation ispermitted during a portion of a trip (218). This includes determiningthe preferred charge/discharge rate for the ESD 60, when engineoperation is compelled during a portion of the trip (234). The preferredcharge/discharge rate is determined based upon the operating conditions,including information related to the current trip and the driving styleof the operator. The operator inputs information into the operatorinterface device 18 related to the current trip, including, e.g.,distance or destination. The control system 15 monitors and determinesthe operator's driving style to optimize the rate of charge depletion ofthe ESD 60. The information is preferably organized in a hierarchicalfashion wherein more specific information permits alteration of thedrive strategy to improve performance. There is a base charge/dischargecalibration, which includes a minimum discharge rate for depletion ofelectric power. The minimum discharge rate is used by the control system15 as the preferred charge/discharge rate in the absence of otherinformation. The minimum discharge rate may minimize fuel usage and/oroperator cost for an expected distribution of trip distances and drivingstyles. The minimum discharge rate may be developed based on astatistical description of vehicle trips in the target vehicle market.

As the vehicle is repeatedly operated, the driving pattern for aspecifically identifiable trip may be characterized statistically interms of speed, acceleration, and number of stops. Alternately, theoperator may select a drive mode via the user input, comprising, forexample, one of city, downtown, rush hour, and cruising mode, with acorresponding preferred charge/discharge rate that is determined for theselected drive mode. Additionally, elevation information as determinedeither from GPS data or from sensors may be used to determine whetherthe terrain is hilly or flat. From this information, the minimumdischarge rate may be modified, for example, to reduce fuel usage forthe driving pattern in use.

In operation, the control system 15 may identify whether a specificallyidentifiable trip in progress. If the specific trip is known, thepreferred charge/discharge rate may be optimized at various points inthe trip to minimize the fuel usage or operating cost. If trip elevationvs. distance is known, this information may be used to optimize thecapture of potential regenerative braking energy during operation of thevehicle. The control system 15 determines a preferred charge/dischargerate comprising a charge depletion rate which accounts for the followingfactors, when known: trip speed vs. distance, total trip length,expected future recharge behavior at end of the trip, and, the tripelevation vs. distance. Various methods may be used to identifyoccurrence of the specific trip, to permit the control system 15 tomonitor and capture information about the trip. This includes theoperator entering trip distance via the operator interface device 18;the operator identifying a specific trip, including selection frompreset list of stored trips, or waypoint identification; the controlsystem 15 matching occurrence of a trip using GPS information; or usinginformation related to speed acceleration, time and, distance.Furthermore, under conditions wherein the vehicle deviates from expectedtrip behavior, preferred charge/discharge rate may be adjusted to takethe deviation into account. Such deviations include, e.g., mismatchesbetween expected and actual speeds, deviations from an expected triproute, and real-time traffic information. In this manner, the baselineor default preferred charge/discharge rate represents a minimum expectedperformance. Vehicle performance is anticipated to improve from the basecharge/discharge rate after a period of learning and adaptation.

When the engine 20 is not compelled to operate, and the EV rangemaximization strategy is not activated, and the charge depletionoperating strategy is not permitted, a charge sustaining operatingstrategy is selected, which comprises setting the preferredcharge/discharge rate to a value that causes the average SOC to track adesired target value (222). When the preferred charge/discharge rate isset to zero, the control system 15 controls operation of the powertrainsystem 10 so that the average state of charge of the ESD 60 is withinmeasurement error of the desired target SOC and within a predeterminedlevel of hysteresis to prevent engine cycling. The desired target SOCneed not be a fixed value and may vary during the course of vehicleoperation taking into account factors such as expected demand for andbattery capability for delivering power and energy, expected supply ofregenerative braking energy due to terrain and/or recharge opportunity,and to minimize the long term exposure of the battery pack to states ofcharge that cause increased rate of degradation or wearout. The engine20 and the first and second electric machines 40 and 50 are controlledto generate electric power and torque to minimize system losses whilemaintaining the state of charge of the ESD 60 (224, 226).

When the preferred charge/discharge rate is determined, e.g., at any oneof (218, 222, 228) the optimal engine state is determined to minimizesystem power loss (224). This includes determining whether thepowertrain operating state includes the engine state as OFF or theengine state as ON, based upon the charge/discharge rate, the conditionsof the ESD 60, and other factors.

The control system 15 determines an optimal operating point at which tocontrol the powertrain system 10 to generate the tractive torque whichis transmitted to the driveline 90, to generate power which istransmitted to the first electric machine 40 to generate electric power,and to regeneratively brake the vehicle and generate electric powerthereby. This includes determining and controlling speed and torqueoutputs from the engine 20 and the first and second electric machines 40and 50 to meet the operator torque request and any requirements forcharging the ESD 60, and to minimize energy usage and power loss in thepowertrain system 10 when controlled to the selected powertrainoperating state, based upon the operator demands, powertrain states, andoperating conditions (226). This operation includes selecting apreferred one of the available powertrain operating states, including,e.g., an electric vehicle operating state, an electrically variabletransmission operating state, an electric vehicle operating state withelectric charging, a charging operating state, a fixed gear operatingstate, and a neutral/charging operating state, depending upon thespecific embodiment of the powertrain system 10 employed. Additionaloperating conditions taken into account include available electricalenergy from the ESD 60. The available electrical energy in the ESD 60 istaken into account in order to minimize the probability that the ESD 60is not discharged below a predetermined minimum state of charge prior toa subsequent charging opportunity. Available electrical energy isdetermined in the BPCM 62 based on the state of charge, the batterytemperature, the battery age, the average temperature history, thecurrent depth of discharge, the cumulative depth of discharge, and thecumulative amp-hour throughput. Vehicle energy usage includes estimatedrolling losses and road loads, which may be monitored and taken intoaccount to modify a projected rate of energy usage. Furthermore, thesystem may use fuel cost information in order to select the most costeffective control between combustible fuel and electricity. The fuel andelectricity costs may be determined based on location, or manuallyentered, or updated via communication with the vehicle from externalsources.

FIG. 4 depicts another embodiment of a powertrain system 10C includingthe engine 20, and an electro-mechanical transmission 30C includingfirst and second electric machines 40 and 50, a first planetary gear set34A, a second planetary gear 34B, and selectively engageable clutches C181, C2 83, C3 85, and C4 87. A first gear member of the gearset 34A, asun gear SA in the present embodiment, is connected to the firstelectric machine 40. A second gear member of the gearset 34A, a ringgear RA in the present embodiment, is connected to the transmissioninput member 24 which in turn is connected to the engine 20. A thirdgear member of the gearset 34A, a double-pinion planet carrier CAconnected to dual-planetary gears PA in the present embodiment, isconnected to the second electric machine 50 and a first gear member ofthe gearset 34B, a sun gear SB in the present embodiment. A second gearmember of the gearset 34B, a planet carrier CB connected to planetarygears PB in the present embodiment, is connected to the transmissionoutput member 64. A third gear member of the gearset 34B, a ring gear inthe present embodiment, may be selectively connected to the transmissioncase (i.e. grounded) via clutch C1 81. The third gear member of thegearset 34B may be selectively connected to the first gear member of thegearset 34A (sun gear SA in the present embodiment) and the firstelectric machine 40 via clutch C2 83. The second electric machine 50 andthe first gear member of the gearset 34B (sun gear SB in the presentembodiment) may be selectively connected the transmission case (i.e.grounded) via clutch C3 85. The second gear member of the gearset 34A(ring gear RA in the present embodiment) and the transmission inputmember 24 (which in turn is connected to the engine 20) may beselectively connected to the third gear member of the gearset 34A(double-pinion planet carrier CA connected to dual-planetary gears PA inthe present embodiment) and to the second electric machine 50 and thefirst gear member of the gearset 34B (sun gear SB in the presentembodiment) via clutch C4 87.

The powertrain system 10C depicted with reference to FIG. 4 isselectively operative in one of several powertrain operating states bycontrolling the engine state and operating the first and second electricmachines 40 and 50 to generate tractive torque which can be transmittedto the driveline 90 via the transmission output member 64 throughselectively applied clutches, as detailed in Table 3.

TABLE 3 Powertrain Operating Clutch State Applied Tractive TorqueGenerator Engine State EV1 C1 second electric machine OFF EV2 C2 firstand second electric OFF machines EVT1 C1 engine and second electric ONmachine EVT2 C2 engine, first and second ON electric machines FG1 C1, C4engine, first and second ON electric machines FG2 C1, C2 engine andsecond electric ON machine FG3 C2, C4 engine, first and second ONelectric machines FG4 C2, C3 engine and first electric ON machineNeutral/ None none ON or OFF Charging

In a first electric vehicle (‘EV1’) operating state, the second electricmachine 50 generates the tractive torque, and the engine state is OFF.In a second electric vehicle (‘EV2’) operating state, the first andsecond electric machines 40 and 50 generate the tractive torque, and theengine state is OFF. In a first electrically variable transmission(‘EVT1’) operating state, the engine state is ON, and the engine 20 andthe second electric machine 50 predominantly generate the tractivetorque, although one having ordinary skill in the art will recognizethat the first electric machine 40 may provide a reaction torquecontributing to the tractive torque. In a second electrically variabletransmission (‘EVT2’) operating state, the engine state is ON, and theengine 20 and the first and second electric machines 40 and 50 generatethe tractive torque. In a first fixed gear operating state (‘FG1’) theengine 20 and the first and second electric machines 40 and 50 generatethe tractive torque. In a second fixed gear operating state (‘FG2’) theengine 20 and the second electric machine 50 predominantly generate thetractive torque. In a third fixed gear operating state (‘FG3’) theengine 20 and the first and second electric machines 40 and 50 generatethe tractive torque. In a fourth fixed gear operating state (‘FG4’) theengine 20 and the first electric machine 40 predominantly generate thetractive torque. In each of the first, second, third, and fourth fixedgear operating states, speed of the transmission output member 64directly corresponds to the engine speed and the fixed gear ratio. Theengine 20 may generate power for charging the ESD 60 through the firstelectric machine 40 during any of the operating states when the enginestate is ON. In a neutral/charging operating state, the engine state canbe ON, with the engine 20 generating power for charging the ESD 60through the first electric machine 40, and disconnected from thedriveline 90, i.e., no tractive torque is transmitted to the driveline90 from the engine 20. Furthermore, the first electrical machine 40 canbe controlled to start the engine 20 in any of the powertrain operatingstates in which the engine state can be ON. Electrical power can beregenerated during braking or coasting events, regardless of thepowertrain operating state.

FIG. 5 depicts another embodiment of a powertrain system 10D includingthe engine 20, and an electro-mechanical transmission 30D includingfirst and second electric machines 40 and 50, a first planetary gear set34A, a second planetary gear 34B, and selectively engageable clutches C181, C2 83, C3 85, C4 87, and C5 89. A first gear member of the gearset34A, a sun gear SA in the present embodiment, is connected to the firstelectric machine 40. A second gear member of the gearset 34A, a ringgear RA in the present embodiment, is connected to the transmissioninput member 24 which in turn is connected to the engine 20. A thirdgear member of the gearset 34A, a double-pinion planet carrier CAconnected to dual-planetary gears PA in the present embodiment, isconnected to the second electric machine 50 and a first gear member ofthe gearset 34B, a sun gear SB in the present embodiment. A second gearmember of the gearset 34B, a planet carrier CB connected to planetarygears PB in the present embodiment, is connected to the transmissionoutput member 64. A third gear member of the gearset 34B, a ring gear inthe present embodiment, may be selectively connected to the transmissioncase (i.e. grounded) via clutch C1 81. The third gear member of thegearset 34B may be selectively connected to the first gear member of thegearset 34A (sun gear SA in the present embodiment) and the firstelectric machine 40 via clutch C2 83. The second electric machine 50 andthe first gear member of the gearset 34B (sun gear SB in the presentembodiment) may be selectively connected the transmission case (i.e.grounded) via clutch C3 85. The second gear member of the gearset 34A(ring gear RA in the present embodiment) and the transmission inputmember 24 (which in turn is connected to the engine 20) may beselectively connected to the third gear member of the gearset 34A(double-pinion planet carrier CA connected to dual-planetary gears PA inthe present embodiment) and to the second electric machine 50 and thefirst gear member of the gearset 34B (sun gear SB in the presentembodiment) via clutch C4 87. The second gear member of the gearset 34A(ring gear RA in the present embodiment) and the transmission inputmember 24 (which in turn is connected to the engine 20) may beselectively connected to the transmission case (i.e. grounded) viaclutch C5 89.

The powertrain system 10D depicted with reference to FIG. 5 isselectively operative in one of several powertrain operating states bycontrolling the engine state and operating the first and second electricmachines 40 and 50 to generate tractive torque which can be transmittedto the driveline 90 via the transmission output member 64 throughselectively applied clutches, as detailed in Table 4.

TABLE 4 Powertrain Operating Clutch State Applied Tractive TorqueGenerator Engine State EV1 C1, C5 first and second electric OFF machinesEV2 C2, C5 first and second electric OFF machines EVT1 C1 engine andsecond electric ON machine EVT2 C2 engine, first and second ON electricmachines FG1 C1, C4 engine, first and second ON electric machines FG2C1, C2 engine and second electric ON machine FG3 C2, C4 engine, firstand second ON electric machines FG4 C2, C3 engine and first electric ONmachine Neutral/ None none ON or OFF Charging

In a first electric vehicle (‘EV1’) operating state, the second electricmachine 50 generates the tractive torque, and the engine state is OFF.In a second electric vehicle (‘EV2’) operating state, the first andsecond electric machines 40 and 50 generate the tractive torque, and theengine state is OFF. In a first electrically variable transmission(‘EVT1’) operating state, the engine state is ON, and the engine 20 andthe second electric machine 50 predominantly generate the tractivetorque, although one having ordinary skill in the art will recognizethat the first electric machine 40 may provide a reaction torquecontributing to the tractive torque. In a second electrically variabletransmission (‘EVT2’) operating state, the engine state is ON, and theengine 20 and the first and second electric machines 40 and 50 generatethe tractive torque. In a first fixed gear operating state (‘FG1’) theengine 20 and the first and second electric machines 40 and 50 generatethe tractive torque. In a second fixed gear operating state (‘FG2’) theengine 20 and the second electric machine 50 predominantly generate thetractive torque. In a third fixed gear operating state (‘FG3’) theengine 20 and the first and second electric machines 40 and 50 generatethe tractive torque. In a fourth fixed gear operating state (‘FG4’) theengine 20 and the first electric machine 40 predominantly generate thetractive torque. In each of the first, second, third, and fourth fixedgear operating states, speed of the transmission output member 64directly corresponds to the engine speed and the fixed gear ratio. Theengine 20 may generate power for charging the ESD 60 through the firstelectric machine 40 during any of the operating states when the enginestate is ON. In a neutral/charging operating state, the engine state canbe ON, with the engine 20 generating power for charging the ESD 60through the first electric machine 40, and disconnected from thedriveline 90, i.e., no tractive torque is transmitted to the driveline90 from the engine 20. Furthermore, the first electrical machine 40 canbe controlled to start the engine 20 in any of the powertrain operatingstates in which the engine state can be ON. Electrical power can beregenerated during braking or coasting events, regardless of thepowertrain operating state.

FIG. 6 depicts another embodiment of a powertrain system 10E includingthe engine 20, and an electro-mechanical transmission 30E includingfirst and second electric machines 40 and 50, a first planetary gear set34A, a second planetary gear 34B, and selectively engageable clutches C181, C2 83, C3 85, C4 87, and C6 91. A first gear member of the gearset34A, a sun gear SA in the present embodiment, is connected to the firstelectric machine 40. A second gear member of the gearset 34A, a ringgear RA in the present embodiment, may be selectively connected to thetransmission input member 24 and a third gear member of the gearset 34Aas described further herein below. The third gear member of the gearset34A, a double-pinion planet carrier CA connected to dual-planetary gearsPA in the present embodiment, is connected to the second electricmachine 50 and a first gear member of the gearset 34B, a sun gear SB inthe present embodiment. A second gear member of the gearset 34B, aplanet carrier CB connected to planetary gears PB in the presentembodiment, is connected to the transmission output member 64. A thirdgear member of the gearset 34B, a ring gear in the present embodiment,may be selectively connected to the transmission case (i.e. grounded)via clutch C1 81. The third gear member of the gearset 34B may beselectively connected to the first gear member of the gearset 34A (sungear SA in the present embodiment) and the first electric machine 40 viaclutch C2 83. The second electric machine 50 and the first gear memberof the gearset 34B (sun gear SB in the present embodiment) may beselectively connected the transmission case (i.e. grounded) via clutchC3 85. The second gear member of the gearset 34A (ring gear RA in thepresent embodiment) may be selectively connected to the transmissioninput member 24 which in turn is connected to the engine 20 via clutchC6 91. The second gear member of the gearset 34A (ring gear RA in thepresent embodiment) may be selectively connected to the third gearmember of the gearset 34A (double-pinion planet carrier CA connected todual-planetary gears PA in the present embodiment) and to the secondelectric machine 50 and the first gear member of the gearset 34B (sungear SB in the present embodiment) via clutch C4 87.

The powertrain system 10E depicted with reference to FIG. 6 isselectively operative in one of several powertrain operating states bycontrolling the engine state and operating the first and second electricmachines 40 and 50 to generate tractive torque which can be transmittedto the driveline 90 via the transmission output member 64 throughselectively applied clutches, as detailed in Table 5.

TABLE 5 Powertrain Operating Clutch State Applied Tractive TorqueGenerator Engine State EV1 C1, C6 second electric machine OFF EV2 C2, C6first and second electric OFF machines EV3 C1, C4 first and secondelectric OFF machines EV4 C2, C4 first and second electric OFF machinesEVT1 C1, C6 engine and second electric ON machine EVT2 C2, C6 engine,first and second ON electric machines FG1 C1, C4, C6 engine, first andsecond ON electric machines FG2 C1, C2, C6 engine and second electric ONmachine FG3 C2, C4, C6 engine, first and second ON electric machines FG4C2, C3, C6 engine and first electric ON machine Neutral/ C6 none ON orOFF Charging

In a first electric vehicle (‘EV1’) operating state, the second electricmachine 50 generates the tractive torque, and the engine state is OFF.In a second electric vehicle (‘EV2’) operating state, the first andsecond electric machines 40 and 50 generate the tractive torque, and theengine state is OFF. In a third electric vehicle (‘EV3’) operatingstate, the first and second electric machines 40 and 50 generate thetractive torque, and the engine state is OFF. In a fourth electricvehicle (‘EV4’) operating state, the first and second electric machines40 and 50 generate the tractive torque, and the engine state is OFF. Ina first electrically variable transmission (‘EVT1’) operating state, theengine state is ON, and the engine 20 and the second electric machine 50predominantly generate the tractive torque, although one having ordinaryskill in the art will recognize that the first electric machine 40 mayprovide a reaction torque contributing to the tractive torque. In asecond electrically variable transmission (‘EVT2’) operating state, theengine state is ON, and the engine 20 and the first and second electricmachines 40 and 50 generate the tractive torque. In a first fixed gearoperating state (‘FG1’) the engine 20 and the first and second electricmachines 40 and 50 generate the tractive torque. In a second fixed gearoperating state (‘FG2’) the engine 20 and the second electric machine 50predominantly generate the tractive torque. In a third fixed gearoperating state (‘FG3’) the engine 20 and the first and second electricmachines 40 and 50 generate the tractive torque. In a fourth fixed gearoperating state (‘FG4’) the engine 20 and the first electric machine 40predominantly generate the tractive torque. In each of the first,second, third, and fourth fixed gear operating states, speed of thetransmission output member 64 directly corresponds to the engine speedand the fixed gear ratio. The engine 20 may generate power for chargingthe ESD 60 through the first electric machine 40 during any of theoperating states when the engine state is ON. In a neutral/chargingoperating state, the engine state can be ON, with the engine 20generating power for charging the ESD 60 through the first electricmachine 40, and disconnected from the driveline 90, i.e., no tractivetorque is transmitted to the driveline 90 from the engine 20.Furthermore, the first electrical machine 40 can be controlled to startthe engine 20 in any of the powertrain operating states in which theengine state can be ON. Electrical power can be regenerated duringbraking or coasting events, regardless of the powertrain operatingstate.

The disclosure has described certain preferred embodiments andmodifications thereto. Further modifications and alterations may occurto others upon reading and understanding the specification. Therefore,it is intended that the disclosure not be limited to the particularembodiment(s) disclosed as the best mode contemplated for carrying outthis disclosure, but that the disclosure will include all embodimentsfalling within the scope of the appended claims.

1. A method for maximizing range capability of a vehicle while operatingin an electric vehicle operating state, said vehicle including apowertrain including an engine and at least one electric machine, themethod comprising: determining an incipient electric vehicle operatingstate of the powertrain; setting a preferred charge/discharge rate of anelectric energy storage device to a maximum charging rate; andcontrolling the powertrain to an operating state including an enginestate that is ON to effect charging the electrical energy storage devicebased on the maximum charging rate.
 2. The method of claim 1 whereincontrolling the powertrain to an operating state including an enginestate that is ON comprises controlling the powertrain to one of anelectrically variable transmission operating state, an electric vehiclewith charging operating state, and a fixed gear operating state.
 3. Themethod of claim 1, wherein controlling the powertrain to an operatingstate including an engine state that is ON comprises selectivelyconfiguring the powertrain as a series hybrid powertrain.
 4. The methodof claim 1, wherein controlling the powertrain to an operating stateincluding an engine state that is ON comprises selectively configuringthe powertrain as a parallel hybrid powertrain.
 5. The method of claim1, wherein determining an incipient electric vehicle operating state ofthe powertrain is based upon proximity of the vehicle to a predeterminedgeographic area.
 6. The powertrain system of claim 5, wherein proximityto the predetermined geographic area is based upon input from anon-board global positioning system.
 7. The powertrain system of claim 5,wherein the predetermined geographic area comprises an area whereatpowertrain operating states are restricted to an electric vehicleoperating state.
 8. The powertrain system of claim 5, wherein thepredetermined geographic area comprises an area identified by anoperator.
 9. A powertrain system for a vehicle, comprising: an engine;an electrical energy storage system including an electrical energystorage device selectively electrically coupled to a remote electricpower source; a transmission including a transmission input memberoperatively connected to the engine, a first electric machineoperatively connected to a transmission output member, a second electricmachine operatively connected to the transmission input member, saidfirst and second electric machines electrically-operatively coupled tothe electrical energy storage system; and a control system implementingan electric vehicle range maximization strategy comprising a) setting apreferred charge/discharge rate to a maximum charging rate, and b)controlling the powertrain to an electric vehicle with electric chargingoperating state to charge the electrical energy storage device based onthe maximum charging rate.
 10. The powertrain system of claim 9, whereinthe powertrain system is permanently configured as a series hybridpowertrain.
 11. The powertrain system of claim 9, wherein the powertrainis selectively configured as a series hybrid powertrain.
 12. Thepowertrain system of claim 9, wherein the transmission furthercomprises: a transmission case; a first selectively engageable torquetransfer device between said first gear member of said first planetarygear set and said transmission case, a second selectively engageabletorque transfer device between said first gear member of said firstplanetary gear set and said first electric machine, a third selectivelyengageable torque transfer device operable when engaged to connect saidfirst electric machine and said transmission input member, atransmission output member connected to said second gear member of saidfirst planetary gear set, and said second electric machine connected tosaid third gear member of said first planetary gear set.
 13. Thepowertrain system of claim 12, wherein the control system implementingan electric vehicle range maximization strategy comprising controllingthe powertrain to the electric vehicle with electric charging operatingstate comprises: controlling said first selectively engageable torquetransfer device engaged, said second selectively engageable torquetransfer device disengaged, and said third selectively engageable torquetransfer device engaged.
 14. The powertrain system of claim 12, whereinthe control system implementing an electric vehicle range maximizationstrategy comprising controlling the powertrain to the electric vehiclewith electric charging operating state comprises: controlling said firstselectively engageable torque transfer device disengaged, and saidsecond and third selectively engageable torque transfer devices engaged.15. The powertrain system of claim 12, wherein the transmission furthercomprises: a second planetary gear set including respective first,second and third gear members; said transmission input member connectedto said first gear member of said second planetary gear set; said secondgear member of said second planetary gear set connected to said firstelectric machine; and said third selectively engageable torque transferdevice between said third planetary gear set member of said secondplanetary gear set and said transmission input member.
 16. Thepowertrain system of claim 15, wherein the control system implementingan electric vehicle range maximization strategy comprising controllingthe powertrain to the electric vehicle with electric charging operatingstate comprises: controlling said first selectively engageable torquetransfer device engaged, and said second and third selectivelyengageable torque transfer devices disengaged.
 17. The powertrain systemof claim 15, wherein the control system implementing an electric vehiclerange maximization strategy comprising controlling the powertrain to theelectric vehicle with electric charging operating state comprises:controlling said first selectively engageable torque transfer devicedisengaged, said second selectively engageable torque transfer devicesengaged, and said third selectively engageable torque transfer devicedisengaged.
 18. The powertrain system of claim 15, wherein the controlsystem implementing an electric vehicle range maximization strategycomprising controlling the powertrain to the electric vehicle withelectric charging operating state comprises: controlling said first andsecond selectively engageable torque transfer devices engaged, and saidthird selectively engageable torque transfer device disengaged.
 19. Thepowertrain system of claim 15, wherein the control system implementingan electric vehicle range maximization strategy comprising controllingthe powertrain to the electric vehicle with electric charging operatingstate comprises: controlling said first selectively engageable torquetransfer device disengaged, and said second and third selectivelyengageable torque transfer devices engaged.
 20. The powertrain system ofclaim 9, wherein the electric vehicle range maximization strategy isimplemented based upon proximity of the vehicle to a predeterminedgeographic area.
 21. The powertrain system of claim 9, wherein: thecontrol system further implements a charge sustaining operating strategysubsequent to the state of charge of the electrical energy storagedevice achieving a predetermined range.
 22. The powertrain system ofclaim 9 wherein: the control system further implements a chargedepleting operating strategy subsequent to implementing the electricvehicle range maximization strategy comprising controlling thepowertrain to an electric vehicle operating state based on one of anoperator demand and proximity of the vehicle to a predeterminedgeographic area.
 23. The powertrain system of claim 21, wherein: thecontrol system further implements a charge depleting operating strategysubsequent to implementing the charge sustaining operating strategycomprising controlling the powertrain to an electric vehicle operatingstate based on one of an operator demand and proximity of the vehicle toa predetermined geographic area.